Mobile telecommunication system

ABSTRACT

This invention relates to a telecommunications system including a plurality of mobile telephones. The telecommunications system has a switch network including: data storage units (HLR) for storing connection data relating to respective mobile telephones; a register (15) for storing associations between the data storage units and respective identification codes; inputs for inputting an identification code; and a switch unit (30, 31) for interrogating the register (15) to determine the data storage unit (HLR) associated with that identification code. The switch network then uses the connection data stored by the data storage unit (HLR) to form a telecommunication link with the corresponding mobile telephone. The associations stored by the register (15) can be changed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a telecommunication system. The presentinvention is particularly, but not exclusively, concerned with atelecommunications system for mobile telephones.

2. Summary of the Prior Art

In standard land-based telecommunications systems, calls are routed fromone fixed point to another, and it is therefore relativelystraightforward to determine a switching path for such calls. Theoriginator of the call inputs information to the system (normally thetelephone number of the destination) in which the routing information isarranged sequentially. Thus, it is relatively straightforward for thesystem to determine the switching necessary to achieve the routing, bysuccessively decoding parts of the input information. Any switchingpoint need consider only part of the information.

When the telecommunication system involves mobile telephones, thesituation is more complicated because a call to a mobile telephone isnot to a fixed point, and therefore the system must determine thelocation of the destination. Currently, a call to a mobile telephoneresults in a signal being transmitted to a data storage unit in the formof a Home Location Register unit (HLR) which determines the location ofthe mobile telephone, and so permits routing of the call to occur.

Inevitably, HLRs have a limited capacity, and some arrangement istherefore necessary to enable telecommunication systems to accessmultiple HLRs. At first sight, all that is needed is for a plurality ofHLRs to be provided, and different mobile telephone numbers assigned todifferent HLRs.

However, this is not consistent with the aim of providing customerflexibility in a mobile telephone system. Each mobile telephone has twotypes of number associated with it, one being the number which thirdparties use to call the mobile telephone (a "MSISDN"), and the otherbeing an identity number (an "IMSI") which is used by thetelecommunications system to address the mobile telephone. Usingexisting techniques, information relating to both of these numbers mustbe stored on the same HLR.

It is envisaged that users may need multiple MSISDN numbers, for exampleif a user is to have the possibility of both voice and datacommunication, in existing systems, any second MSISDN number with acommon identity number (IMSI) must be a MSISDN number of the same HLR asthe previous MSISDN number. This could be impossible to achieve if, forexample, the HLR containing the original information is full. Then theonly way that additional services could be provided would require theuser to change telephone number, which would be undesirable. Thisbecomes a particular problem if it is desirable that users are able toselect their numbers, rather than be provided with them.

SUMMARY OF THE INVENTION

To overcome these problems, the present invention proposes that theswitch network which connects users to other users, HLRs, and systemservices, has a register unit associated therewith, which register unitcontains information relating each telephone number to a correspondingone of a plurality of HLRs. The relationship between telephone numbersand HLRs should then be freely selectable within the register unit, sothat the register unit acts as a converter between the number and theinformation identifying the HLR.

By providing such a register unit, the fixed relationship betweennumbers and HLRs is broken, and any number may be assigned to any HLR,assuming space permits.

The register unit may also store further information associated with themobile telephones which permits the switch network to enable calls frommobile telephones to be routed to different services, depending on thecalling mobile telephone itself, in addition to the number dialled.

As a first example, different mobile telephones provided by differentorganisations (Service Providers) could use the same generic access codee.g. 150, to call the parent Service Provider regarding billing queriesfor example. It is convenient if such services are accessed by numberswhich are independent of the organisation providing the service. Then, acall from a mobile telephone to such a service triggers a signal to theregister unit which generates information which identifies the serviceunit associated with that number for the particular mobile telephone.That identification information may then be passed back to the switchnetwork to enable the call to be routed to the correct service unit.

As a second example, users could be able to access voice mail inrespective personal mail boxes by dialling a second generic access code,say 123, the register providing information necessary for routing of thecall.

In either case, the system may be adapted so that if the user is using apublic telephone, rather than his own mobile phone, he can conveymanually to the switch network information sufficient for the switchnetwork to obtain from the register the further information associatedwith the user's mobile telephone.

A further possibility is for the register to use the further informationconcerning the mobile telephones in relation to calls to the telephones,rather than from the telephones. For example, the further informationmay be sufficient to redirect a telecommunications link originallydestined for a given mobile telephone if that phone is unavailable,perhaps because it is engaged or inoperative or because its owner doesnot answer. Such a system may for example be capable of operating suchthat if a person attempts to contact a mobile phone which isunavailable, the switch network can redirect the call to an appropriateservice, such as a voice mail service.

By using the present invention, many advantageous features of thetelecommunication system can be achieved. If there is any failure in theunit of the mobile telephone which identifies the mobile telephone (thatunit being referred to as a SIM), it should be possible to replace thatunit quickly. With the present invention, even if the new identitynumber IMSI provided to the user relates to a different HLR from theprevious identity number IMSI, the user need not change their telephonenumber (MSISDN number), since the reassignment to the new HLR may beachieved by the register unit.

Hence, any telephone number (MSISDN number) may be mapped onto any useridentity.

An embodiment of the present invention will now be described in detail,by way of example, with reference to the accompanying drawings, inwhich:

FIG. 1 is a schematic block diagram of a telecommunication systemincorporated in the present invention; and

FIG. 2 shows part of the telecommunication system of FIG. 1 in moredetail.

DETAILED DESCRIPTION

Referring first to FIG. 1, a switched network 10 interconnectsland-based and mobile telephones. If a call to a mobile telephone ismade from a land-based telephone, the call is routed via the publicswitch telephone network (PSTN) 11 to the switch network, and from thatswitch network 10 to the mobile telephone (BSS) 12. To do this, theswitch network 10 must determine routing information, and to determinethat routing information it must determine the location of the mobiletelephone 12, which it does via a HLR to which the mobile telephone 12is associated. When there are multiple HLRs 13,14, it is necessary forthe switch network 10 to determine which HLR 13,14 must be accessed, onthe basis of the telephone number (MSISDN number) of the mobiletelephone input by the originator of the call.

In accordance with the present invention, the switch network 10 accessesa register unit 15, which identifies the called number and addresses itto a particular HLR 13,14 with which the mobile telephone 12 isassociated. The register unit 15 permits the relationship between anygiven mobile telephone number and the HLRs 13,14 to be determinedfreely, so that the number is unaffected by the particular HLR 13,14with which it is associated. The register unit 15 removes the need for aparticular mobile telephone number to be associated with a fixed HLR13,14.

Once the particular HLR 13,14 with which the mobile telephone 12 isassociated has been identified, signalling can occur to that HLR, andinformation derivable therefrom, in the usual way. This information isused to "set-up" the call to the mobile telephone 12, which may then berouted to the destination telephone as is normal.

Similarly, if a call originates at the mobile telephone 12, the switchnetwork 10 must again determine the routing of that call. If the call isto a land-based telephone, connected to the switch network 10 via thePSTN 11, then this routing can be on the basis of the telephone numberof the destination telephone, in the normal way.

If a call is made from a mobile telephone 12 to one of a plurality ofvoice processing systems 16,17 or to services 18 associated with theswitch network using a short code (e.g. 123) the relationship betweenthe mobile telephone 12 and the corresponding service must be determinedby the register unit 15 before the switch network can determine theappropriate voice processing system 16,17 or services 18 to be accessed.

It should be noted that existing systems are similar to the arrangementshown in FIG. 1, but without the register unit 15 and with only a singleHLR. Such existing systems do not need to determine which HLR is to beaccessed, since there is only one such HLR. To achieve the presentinvention, the switch network 10 accesses the register unit 15 whenhandling any call that would result in a signalling enquiry to the HLRin the existing arrangements, to determine which of the multiple HLRs13,14 is to be accessed. Hence, the present invention can be achieved bythe provision of the register unit 15, and suitable programming of theswitch network 10.

FIG. 2 shows the switch network 10 in more detail. It will have aplurality of mobile switching centres (MSC) 20,21 and 22, and a calldestined to any given mobile telephone results in signalling betweenthat MSC 20 to 22 and one of a plurality of signalling transfer points(STP) 30,31, which signal to the register unit 15 to determine the HLR13,14 which is appropriate to the mobile telephone 12. The register unit15 determines that information from the telephone number (MSISDN number)of the mobile telephone 12. It would then be possible for the registerunit 15 to forward the signal directly to the appropriate HLR 13,14 but,as shown in FIG. 2, it is preferable that the information is passed backto the corresponding STP 30,31 which then passes the signalling to thecorrect HLR 13,14.

A similar signalling flow is seen when the user of the mobile telephone12 tries to access one of the voice processing systems (VPS) 16,17. Thecall is received by one of the MSCs 20,21 and 22 which passes thedialled digits and the identity of the mobile telephone to one of theSTPs 30,31,32. This relays the information to the register unit 15,which uses this information to construct the correct address of theappropriate voice processing service (VPS) 16,17. That information isrelayed back from the register unit via one of the STPs 30,31,32 to theoriginal MSC 20,21,22. This address is then used to route the call bythe switch network 10. That routing passes the call from the appropriateMSC 20,21,22 via the switch network (comprising transit switchingcentres, TSCs 32,33) to the appropriate VPS 16,17.

The signal which a mobile telephone passes to the switch network, and bywhich the mobile telephone is recognised, need not be fixed, but may bealterable, for example by insertion into the telephone of a cardcarrying data. Thus, a user can identify himself or herself to theswitch network by insertion into a mobile telephone of a personal cardwhich identifies him or her, and subsequent routing to an appropriateVPS can be performed on the basis of the user's identity.

The facility of routing calls to VPS using information in the registerunit 15 will enable the location of individual voice processing services(such as mailbox accounts) at locations which have the closestgeographical proximity to where the mobile telephone will predominantlybe located. This can dramatically reduce the cost of calltransportation.

Moreover, if the predominant location of the mobile telephone changes,so that it is more convenient to use a different VPS 16,17, then thischange can be logged in the register unit 15. The calling subscriber canstill access his VPS account (although now hosted by a differentplatform) without changing the number used to call the service.Similarly, if the user of the mobile telephone changes from one serviceprovider to another, the register unit 15 can accommodate this changewithout the user having to dial different numbers. Thus, for example,where there are several service providers and the user of the mobiletelephone changes from one service provider to another, it is notnecessary for that user to dial different numbers to reach the newservice provider. Instead, the same numbers can be used and the newrouting of the call is controlled by the signals passed between the MSC20,21,22 and the register unit 15.

The switch network 10 may also use the information about the mobilephones so that if a given phone is engaged, unanswered or inoperative,the switch network can redirect calls originally directed to that phoneto an appropriate VPS, such as a voice message system.

We claim:
 1. A switch network for a telecommunication system including aplurality of mobile telecommunication devices, the switch networkcomprising:a plurality of data storage units for storing connection datarelating to one or more respective telecommunication devices and fordetermining the location of said one or more respective mobiletelecommunication devices; a register unit common to the data storageunits for storing associations between the data storage units and one ormore respective identification codes; input means for inputting anidentification code; a switch unit for interrogating the register unitto determine the data storage unit associated with that identificationcode; link means for using the connection data stored by that datastorage unit to form a telecommunication link with one of thecorresponding one or more mobile telecommunication devices; and meansfor altering the associations stored by the register unit; wherein thelink means is configured to bypass the register unit to form a link withthe corresponding one or more mobile telecommunication devices using theconnection data once the data storage unit associated with thatidentification code has been determined.
 2. A switch network accordingto claim 1 wherein the connection data is location data indicating thelocation of the corresponding one or more telecommunication devices. 3.A switch network according to claim 1 in which the register unit storesfurther information associated with the telecommunication devices, theswitch network including means for interrogating the register unit inresponse to a signal to extract the further information associated witha specified telecommunication device, the link means forming atelecommunications link in dependence upon said further information. 4.A switch network according to claim 3 further comprising means forchanging said further information.
 5. A telecommunication systemcomprising:a plurality of mobile telecommunication devices; and a switchnetwork comprising:a plurality of data storage units for storingconnection data relating to one or more respective telecommunicationdevices and for determining the location of said one or more respectivemobile telecommunication devices; register unit common to the datastorage units for storing associations between the data storage unitsand one or more respective identification codes; input means forinputting an identification code; a switch unit for interrogating theregister unit to determine the data storage unit associated with thatidentification code; link means for using the connection data stored bythat data storage unit to form a telecommunication link with one of thecorresponding one or more mobile telecommunication devices; and meansfor altering the associations stored by the register unit; wherein thelink means is configured to bypass the register unit to form a link withthe corresponding one or more mobile telecommunication devices using theconnection data once the data storage unit associated with thatidentification code has been determined.
 6. A telecommunication systemaccording to claim 5 wherein at least some of said telecommunicationdevices are associated with services provided to the user.
 7. A switchnetwork for a telecommunication system including a plurality of mobiletelecommunication devices, the switch network comprising:a plurality ofdata storage units which are configured to store connection datarelating to one or more respective telecommunication devices and whichare configured to determine the location of said one or more respectivemobile telecommunication devices; a register unit common to the datastorage units which is configured to store associations between the datastorage units and one or more respective identification codes; an inputsystem which is operable to input an identification code; a switch unitconfigured to interrogate the register unit to determine the datastorage unit associated with that identification code; a linking systemarranged to use the connection data stored by that data storage unit toform a telecommunication link with one of the corresponding one or moremobile telecommunication devices; and an alteration system arranged toalter the associations stored by the register unit; wherein the linkingsystem is configured to bypass the register unit to form a link with thecorresponding one or more mobile telecommunication devices using theconnection data once the data storage unit associated with thatidentification code has been determined.